Assessment of Single and Two-Phase Models for Nanofluid Flow at the Entrance Region of a Uniformly Heated Tube

2012 ◽  
Author(s):  
Sinan Goktepe ◽  
Kunt Atalik ◽  
Hakan Erturk
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Friction Factor ◽  
Convective Heat ◽  
Control Volume ◽  
Convective Heat Transfer Coefficient ◽  
Computational Cost ◽  
Nanofluid Flow ◽  
Two Phase ◽  
Phase Models

Hydrodynamic and thermal characteristics of Al2O3 – water nanofluid flow at entry region of a uniformly heated pipe are studied applying finite control volume method (FCV). Single phase and Eulerian-Eulerian two-phase models were used in modelling of nanofluid flow and heat transfer. The two methods are evaluated by comparing predicted convective heat transfer coefficients and friction factor with experimental results from literature. Solutions with two different velocity pressure coupling algorithms, Full Multiphase Coupled, and Phase Coupled Semi-Implicit Method for Pressure Linked Equations are also compared in terms of accuracy and computational cost. Two-phase model predicts convective heat transfer coefficient and friction factor more accurately at the entry region. Moreover, computational cost can be reduced by implementing Full Multiphase Coupled scheme.

Experimental Investigation of Single-Phase Convective Heat Transfer of Nanofluids in a Minichannel

2010 ◽  
Author(s):  
Dong Liu ◽  
Leyuan Yu
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Convective Heat Transfer ◽  
Friction Factor ◽  
Convective Heat ◽  
Single Phase ◽  
Convective Heat Transfer Coefficient ◽  
Transition To Turbulence ◽  
Scaling Analysis ◽  
Transition Flow

Nanofluids have been proposed as a promising candidate for advanced heat transfer fluids in a variety of important engineering applications. A consensus is now lacking on if and how the dispersed nanoparticles alter the thermal transport in convective flows. An experimental investigation was conducted to study single-phase forced convection of Al2O3-water nanofluid in a circular minichannel. The friction factor and convection heat transfer coefficients were measured for nanofluids of various volume concentrations (up to 5%) and were compared to these of the base fluid. The Reynolds number varied from 600 to 4500, covering the laminar, transition and early fully developed turbulent regions. It was found that the nanofluids exhibit pronounced entrance region behaviors in the laminar region. In the transition and turbulent regions, the onset of transition to turbulence is delayed in nanofluids. Further, both the friction factor and convective heat transfer coefficient are below these of water at the same Re in the transition flow. Once fully developed turbulence is established, the difference in the flow and heat transfer of nanofluids and water will diminish. A scaling analysis showed these behaviors may be attributed to the variation in the relative size of nanoparticle with respect to the turbulent microscales. This work suggests that the particle-fluid interaction has a significant impact on the flow physics of nanofluids, especially in the transition and turbulent regions. Consequently, nanofluids should be used in either the laminar flow or fully developed turbulent flow at sufficiently high Re in order to yield enhanced heat transfer performance.

Comparisons of single-phase and two-phase models for numerical predictions of Al2O3/water nanofluids convective heat transfer

2020 ◽  
Vol 31 (7) ◽  
pp. 3050-3061
Author(s):  
Zhaoping Ying ◽  
Boshu He ◽  
Di He ◽  
Yucheng Kuang ◽  
Jie Ren ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Single Phase ◽  
Two Phase ◽  
Numerical Predictions ◽  
Phase Models

Simulation Research of Heat Transfer Characteristics of Carbon Dioxide in Microchannel Evaporator

2018 ◽  
Vol 10 (6) ◽  
Author(s):  
Lv Jing ◽  
Shi Dongdong ◽  
Wang Taisheng ◽  
Fu Yijun ◽  
Li Chang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Phase Region ◽  
Heat Transfer Characteristics ◽  
Two Phase ◽  
Simulation Results ◽  
Dry Out

Abstract In this paper, the simulation model of two-dimensional (2D) distribution parameter of a CO2 microchannel evaporator was developed using the finite element method. The simulation model of the CO2 microchannel evaporator was written using matlab both considering the dry and wet conditions on air side, and different heat transfer characteristics of CO2 in two-phase region and overheated region. The experimental and simulation results in terms of CO2 temperature, wall temperature, inlet and outlet air temperatures, and convective heat transfer coefficient were compared. The simulation results have the same tendency with the experimental correlation results. The convective heat transfer efficient increases with the growth of CO2 inlet dryness, mass flow rate and air speed, while decreases along with the increase of evaporation pressure in two-phase region. The dry-out point appears earlier with larger CO2 inlet dryness, and higher air temperature, humidity and speed; however, it appears later with the increasing evaporation pressure and mass flow rate. The convective heat transfer coefficient at the dry-out point decreases dramatically due to the deteriorated heat transfer at this position, which indicates the necessity to prevent or retard the appearance of dry-out point.

A comparative analysis on the single-phase and two-phase mixture models for calculation of ferrofluid convective heat transfer in the presence of a magnetic field: a numerical study

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hamed Jafari ◽  
Mohammad Goharkhah ◽  
Alireza Mahdavi Nejad
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Single Phase ◽  
Numerical Study ◽  
Phase Method ◽  
Two Phase ◽  
Content Type ◽  
Phase Models

Purpose This paper aims to analyze the accuracy of the single and two-phase numerical methods for calculation of ferrofluid convective heat transfer in the presence of a magnetic field. The findings of current study are compared with previous single-phase numerical results and experimental data. Accordingly, the effect of various parameters including nanoparticles concentration, Reynolds number and magnetic field strength on the performance of the single and two-phase models are evaluated. Design/methodology/approach A two-phase mixture numerical study is carried out to investigate the influence of four U-shaped electromagnets on the hydrodynamic and thermal characteristics of Fe3O4/Water ferrofluid flowing inside a heated channel. Findings It is observed that the applied external magnetic field signifies the convective heat transfer from the channel surface, despite local reduction at a few locations. The maximum heat transfer enhancement is predicted as 23% and 25% using single and two-phase models, respectively. The difference between the results of the two models is mainly attributed to the slip velocity effect which is accounted for in the two-phase model. The magnetic field gradient leads to a significant increase in the slip velocity which in turn causes a slight difference in velocity and temperature profiles obtained by the single and two-phase models in the magnetic field region. According to percentage error calculation, the two-phase method is generally more accurate than the single-phase method. However, the percentage error of both models improves by decreasing either magnetic field intensity or Reynolds number. Originality/value For the first time in the literature, to the best of the authors’ knowledge, the current work analyzes the accuracy of the single and two phase numerical methods for calculation of ferrofluid convective heat transfer in the presence of a magnetic field.

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